what is the difference between continuous feature and pattern feature
what is the difference between continuous feature and pattern feature
(OP)
Hi,
Use fig.2-8 as an example. If I specify 2X ø22.1, 22.2 to the shaft diameter, would it be different from ø22.1, 22.2 <CF>?
Thanks in advance.
Use fig.2-8 as an example. If I specify 2X ø22.1, 22.2 to the shaft diameter, would it be different from ø22.1, 22.2 <CF>?
Thanks in advance.





RE: what is the difference between continuous feature and pattern feature
One of those diameters could be up a little, and then after the groove the next one could be down a little. Using CF treats them as one feature, thus Rule #1 will keep them coaxial within the size limits.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: what is the difference between continuous feature and pattern feature
If I specify same positional tolerance to the two different size callouts, ie,
2X ø22.1, 22.2
|pos|ø0.5|A|B|C|
vs.
ø22.1, 22.2 <CF>
|pos|ø0.5|A|B|C|
Would the positional tolerance zones or inspection process in the two be different?
RE: what is the difference between continuous feature and pattern feature
So with your position tolerance of 0.5, but no CF, one of the diameters could be 0.25 up and the other diameter could be 0.25 down (yet both axes could still be horizontal). In other words, this step would be allowed; it would not be seen as a form error violating Rule #1.
But the position tolerance of 0.5, and WITH the CF, they couldn't have that step of 0.5 -- they would be controlled as in-line with each other to the amount of the size tolerance.
Without using CF, we could take your suggestion and transform it into a composite feature control frame:
2X ø22.1, 22.2
|pos|ø0.5|A|B|C|
| |ø0.1|
I think this would be identical to having CF with the single position tolerance.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: what is the difference between continuous feature and pattern feature
2X DIA 22.2/22.1
POS|DIA.00(M)
?
RE: what is the difference between continuous feature and pattern feature
I mentioned the composite FCF only because I was trying to show how the position tol suggested by bxbzq wouldn't achieve the intended result.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: what is the difference between continuous feature and pattern feature
I'm not a vegetarian because I dislike meat... I'm a vegetarian because I HATE plants!!
RE: what is the difference between continuous feature and pattern feature
If the positional tolerance is applied on rfs basis, as long as the positional tolerance is smaller than the size tolerance, the two different callouts (2X vs. <CF>) would mean the same.
If the positional tolerance is applied on mmc basis, the positional tolerance has to be zero to make the two callouts mean the same.
RE: what is the difference between continuous feature and pattern feature
As for the latest query --
No, because without the CF, each of the diameters (separated by the groove) could be within position tolerance and within their own size tolerance, but the virtual condition could be larger than the maximum size.
Yes, I think this would be correct.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: what is the difference between continuous feature and pattern feature
I'm not a vegetarian because I dislike meat... I'm a vegetarian because I HATE plants!!
RE: what is the difference between continuous feature and pattern feature
Could you please take a look at Fig. 2-8 ASME Y14.5-2009 (The one that actually started this conversation) and tell if it looks like 1 feature to you?
(Same applies to Fig. 2-9 and 2-10 as well)
The whole point of this thread is to discuss different ways to make 2 or more features behave like one. (Or at least that's how I see it)
RE: what is the difference between continuous feature and pattern feature
Did you mean outer boundary? If this is the case I think you are right.
Think it through, CF is a more restrict requirement. When applied at rfs, if the two diameters are produced at mmc, the CF callout would require the two diameters to be perfectly aligned to each other, while the 2X callout still allows one diameter offset 0.1 from the other one.
RE: what is the difference between continuous feature and pattern feature
And yes, CF is more restrictive, but that's what it's intended for. (It's pretty much Rule #1 extended to multiple features.)
We should only use CF when we want the alignment to operate within the size; if it's OK for the two diameters to stray apart beyond an MMC envelope, then position of some non-zero value should be used.
John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems
RE: what is the difference between continuous feature and pattern feature
RE: what is the difference between continuous feature and pattern feature
I'm not a vegetarian because I dislike meat... I'm a vegetarian because I HATE plants!!